As a conventional cage of a hub unit bearing, there is known an inclined cage which is formed in a tapered cylindrical shape and in which a plurality of pockets which hold rolling elements are provided at equal intervals in a circumferential direction at the middle of an axial width of the cage (see, JP-A-H08-014258). The cage is molded from synthetic resin, and includes inclined pillar portions provided between pockets, a small-diameter side annular portion which is a portion on a smaller diameter side of the pockets, and a large-diameter side annular portion which is a portion on a larger diameter side of the pockets. An inner diameter surface and an outer diameter surface of the respective small-diameter side annular portion and large-diameter side annular portion are formed in a cylindrical surface shape.
As the other conventional inclined cage, an inclined crown cage is known (see, e.g., JP-A-2008-115981). The cage has a hollow annular shape which is continuously tapered and diameter-shrunk from the large diameter side toward the small diameter side and is formed into a substantially truncated cone shape as a whole. A plurality of pockets which rotatably hold a plurality of rolling elements one by one are formed on the cage at equal intervals along the circumferential direction, and openings for inserting the rolling elements one by one from the large diameter side to the pockets is formed on the large diameter side.
The cage described in the above JP-A-H08-014258 and JP-A-2008-115981 is set in a state where a plurality of cages are stacked on a cage stocker (not shown) along an axial direction in a production line of a bearing. Therefore, before being set in the cage stocker, the plurality of cages are packaged in a stacked state (straight winding packaging).
In general, the inclined cage and the inclined crown cage as described above are manufactured by axial draw injection molding. Therefore, an outer diameter of the small-diameter side annular portion is smaller than an inner diameter of the large-diameter side annular portion, and when the cages are stacked by straight winding packaging or the like, the outer diameter of the small-diameter side annular portion is in contact with a thin portion of the inner diameter of a tapered pillar portion. When a force acts on the cages in the axial direction in this contact state, the thin portion of the inner diameter of the pillar portion is deformed or the outer diameter of the small-diameter side annular portion is fitted to the thin portion of the inner diameter of the pillar portion, so that there is a possibility that separation of the cage may be difficult in the cage stocker. The problem of this fitting is particularly occurring in the inclined crown cage.
In order to solve this problem, in the cage described in JP-A-2008-115981, a recessed portion is provided on an end surface on a large-diameter side, and an end portion on a smaller-diameter side is extended toward an axially outer side. When the cages are stacked, the end portion on the smaller diameter side of the adjacent cage is placed on the recessed portion.
However, in JP-A-2008-115981, since the cross-sectional area of the cage is increased, a contact angle of rolling elements is large, and it is difficult to use as a cage of a bearing having a high shoulder portion adjacent to a raceway groove. Since the cage is long in the axial dimension, the number of cages in a straight winding packaged state is decreased, so that the interval of supplying the cages to the cage stocker is shortened, which may increase the man-hour of workers.